1. Field of the Invention
The present invention relates to a heat collector for solar thermal power generation.
2. Description of the Related Art
Solar thermal power generation is a technique of collecting solar light into a heat collector using a mirror and a lens, heating a heat medium in the heat collector, and rotating a turbine with steam generated by thermal exchange with the heated heat medium so as to generate power. Conventionally, a heat collector for solar thermal power generation using silicon carbide ceramics has been proposed (for example, see Patent Document 1: Japanese Patent Application Laid-open No. 2012-92688). The heat collector made of ceramics has an advantage that it is excellent in heat resistance in comparison with a heat collector made of a metal. In particular, silicon carbide ceramics has a high heat conductivity and a low thermal expansion coefficient. Therefore, the silicon carbide ceramics is excellent in thermal shock resistance and is appropriate as a heat collector the temperature of which becomes extremely high with light collection of solar light.
There is, however, a problem that silicon carbide is oxidized when heated to a high temperature under presence of oxygen. It is said that when the surface of silicon carbide is covered by a film of silicon dioxide generated by oxidation of silicon carbide, further oxidation is suppressed to some extent. However, the suppression of oxidation with the film of silicon dioxide is insufficient in fact.